The classical cannabinoid Δ9-Tetrahydrocannabinol (Δ9-THC) is the major active constituent extracted from Cannabis sativa. The effects of this, and other, cannabinoids are due to an interaction with specific, high-affinity receptors. Presently, two cannabinoid receptors have been characterized: CB1 and CB2. Characterization of these receptors has been made possible by the development of specific synthetic ligands such as the agonists WIN 55212-2 and CP 55,940.
Additionally, recent scientific discoveries have demonstrated that the endocannabinoid system is very extensive and is currently under intense investigation. Radiochemical methods have been in use for more than a decade for studying the complex phenomena associated with the endocannabinoid system and cannabimimetic molecules. Despite the usefulness and sensitivity of radiochemical methods, the use of alternative methods such as fluorescence techniques can provide information not readily accessible by conventional radiochemical methods and circumvent certain drawbacks associated with them, such as high cost, special precautions in handling and disposal and potential health hazards. Fluorescent approaches provide great advantages over radiochemical methods in accuracy, sensitivity, efficiency, safety and a wide scope of additional applications, and generally are less costly than radiochemical methods. The state-of-art fluorescence approaches enable researchers to detect particular components of complex biomolecular assemblies, including living cells. In particular the emission spectrum of a fluorescer is sensitive to its environment. Therefore, fluorescence approaches are extremely useful in providing spatial, dynamic and temporal information about the interactions between marcomolecules and their ligands.
With the help of available fluorescent ligands, fluorescence techniques have successfully been applied to study the behavior of a number of biological macromolecules, including dopamine receptors, histamine receptors, muscarinic receptors, adrenergic receptors, glucagon receptors, opiate receptors, adenosine receptors and serotonin receptors. The applications of receptor-specific fluorescent ligands are considerably broad, such as molecular studies on ligand-induced conformational changes within the receptor, rapid kinetics of ligand-receptor interactions, the localization of the ligand-binding site on the receptor and distances between different binding sites on the same receptor. Moreover, fluorescent ligands have been successfully used for studying the mobility of some receptors in both normal and pathophysiological conditions by fluorescence photobleach recovery techniques, and to localize receptors at tissue and cellular level by fluorescence microscopic techniques. Furthermore, receptor-specific fluorescent ligands have been employed for receptor assays including the determination of the receptor dissociation constant (KD) and the total receptor content of the tissue (Bmax) by fluorescence titration techniques.
In general, fluorescent ligands are prepared by linking parent ligands with fluorescent moieties to make the newly formed ligands detectable or measurable by fluorescence techniques. Such strategies often face the challenge of reduced potency or efficacy of the parent ligands during interaction with target macromolecules. The inventors are not aware of cannabinoid compounds having fluorescence properties.